Electrical service providers such as electrical utilities employ electricity meters to monitor energy consumption by customers (or other entities). Electricity meters track the amount of energy consumed a load (e.g. the customer), typically measured in kilowatt-hours (“kwh”), at each customer's facility. The service provider uses the consumption information primarily for billing, but also for resource allocation planning and other purposes.
Electrical power is transmitted and delivered to load in many forms. For example, electrical power may be delivered as polyphase wye-connected or delta-connected power or as single phase power. Such various forms are known as service types. Different standard electricity meter types, known as meter forms, are used to measure the power consumption for the various service types. The commonly used meter forms in the United States include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.
Electrical service providers have historically billed for electrical service in arrears, using information stored within the electricity meter to determine the amount of each invoice. In a typical operation, the electricity meter stores a value representative of the amount of energy consumed in a mechanical or electronic accumulation register. From time to time, the electrical service provider obtains the value of the register and bills the customer accordingly. For example, a meter reader employed by the service provider may, each month, physically read the register value off a meter display. The service provider then employs the obtained register value to determine the amount of electricity consumed over the month and bills the customer for the determined amount.
A problem with the above-described operation of electrical service providers arises from the fact that some customers are frequently delinquent in or, in default of, payments for electricity consumption. Delinquent payments can result in significant losses for the service provider. Accordingly, it is often necessary to interrupt the delivery of electrical power to some customers before losses to the service provider become excessive.
Interrupting the delivery of electrical power has historically been an expensive and significant event. Typically, a technician must be dispatched to the customer's residence, or in the vicinity thereof, to physically disconnect the power. Accordingly, while the electrical service provider might physically disconnect the power to the customer's facility for several months of complete payment default, physical disconnection is not practical in circumstances in which customers are merely delinquent, or that can only pay portions of their bills. In particular, the cost and effort of sending a technician out to disconnect electrical service is wasted if the customer pays a day or two later, thereby requiring another service call to restore service.
One method of controlling losses associated with delinquent customers is to require prepayment for services. In prepayment arrangements, customers use prepaid debit cards or credit cards to “purchase” energy in advance. When the purchased energy has been consumed, the electrical service is disconnected. Thus, the service provider is not exposed to extended periods of electrical service for which no payment may be provided. Another method of handling delinquent customers is to intermittently interrupt power to delinquent customers until the past due payments are made. Intermittent interruptions tend to reduce the amount of energy consumed by the delinquent payor, thus advantageously reducing utility provider losses while also reducing bills to the delinquent payor.
Each of the above methods, however, typically requires the ability to disconnect and/or reconnect the customer's power without a technician service call to the customer's location. For example, in a prepayment scenario, the service provider must have a method of disconnecting power once the prepaid amount of energy has been consumed. Similarly, the intermittent interruption technique requires frequent connection and disconnection of the electrical service.
One technique for automated or remote service disconnection is to employ a service disconnect switch device within an electricity meter. The service disconnect switch is a relay or other device that controllably disconnects and re-connects the utility power lines to the customer's feeder lines, thereby controllably interrupting power to the customer's facility. In some cases, the service disconnect switch is tripped by a remote device that communicates with the electricity meter circuitry through a modem, radio or the like. Alternatively, such as in the case of prepayment, the meter itself may be programmed to disconnect and reconnect electrical service under certain circumstances. In some situations, the meter may disconnect and restore electrical service through a combination of local programming and remote commands.
Thus, the inclusion of a service disconnect switch within a meter facilitates various methods and techniques for providing electrical service to parties that have poor payment records. The service disconnect switch is typically an electromechanical relay capable of handling the meter AC rated currents, for example, 100 A rms or 200 A rms. The use of a service disconnect switch advantageously may not require a permanent disconnection by a field technician. The conveniences provided by a service disconnect switch also extends beyond use in connection with delinquent payors. For example, electrical energy rationing may be implemented using techniques enabled by the service disconnect switch.
Nevertheless, various issues that arise from the use of a service disconnect switch have not been adequately addressed in the prior art. For example, in a traditional service disconnect application, upon receiving a command to open or close the service disconnect switches, the micro controller immediately drives the relays control coils to execute the command. However, after the open or close command is given, some time delay is required for the electromechanical relays to operate. Only after this time delay is the electrical disconnect switch finally opened or closed. The time when the relay contacts actually open or close is not known in current arrangements. The relay contacts may open or close when the AC line voltage is at or close to its peak voltage, causing a significant temperature rise in the contacts and arcing that deteriorates prematurely the contacts. This situation reduces the life of the relays over time and increases the temperature rise inside the electricity meter.
In view of the foregoing, there is a need for an electricity meter that employs service disconnect switch and that avoids one or more of the above described drawbacks. In particular, a need exists for an electricity meter that includes a service disconnect switch having increased safety enhancements associated with disconnecting and reconnecting a customer's electrical service. In particular, a need exists for an electricity meter with a disconnect switch that that operates efficiently without significant temperature rise in the contacts or deterioration of the contacts over time. It would also be advantageous if such electricity meter with a disconnect switch were capable of handling disconnects in both single phase and multiple phase power lines over many open/close cycles while reducing wear of the relay over time.